Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Oct. 01, 2021	Oct. 01, 2021	Oct. 02, 2020	Dec. 31, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Net earnings (loss)	$ 14,667	$ 34,507	$ (38,322)
Earnings from discontinued operations, net of tax	0	0	692
Earnings from continuing operations	14,667	34,507	(39,014)
Adjustments to reconcile net earnings from continuing operations to net cash provided by (used in) operating activities of continuing operations:
Depreciation and amortization		27,474	32,204
Amortization of debt issuance costs		1,406	1,325
Accretion of convertible notes discount		2,191	2,132
Provision for doubtful accounts		373	570
Goodwill, Impairment Loss	0	0	50,307
Gain (Loss) on Disposition of Business	0	234	(493)
Net (gain) loss on sale of assets	(31)	(16)	(5)
Net loss on derivative instruments		815	144
Stock compensation expense	1,459	5,684	4,254
Deferred income taxes		4,822	6,590
Changes in assets and liabilities, excluding effects of acquisitions/divestitures:
Accounts receivable		71,434	(19,556)
Increase (Decrease) in Contract with Customer, Asset		(19,940)	(5,085)
Contract costs		(99)	(48)
Inventories		(12,435)	(18,273)
Income tax refunds receivable		3,145	(4,431)
Operating Right-of-Use Assets		1,739	427
Other assets		1,042	526
Accounts payable - trade		(21,829)	(18,258)
Contract liabilities		(24,036)	(26,165)
Operating Lease Liabilities		(1,810)	(498)
Payments for Retention Plans		(25,108)	0
Other current liabilities		(2,698)	5,997
Income taxes payable		1,173	(3,464)
Pension liabilities		(29,256)	(18,662)
Increase (Decrease) in Other Noncurrent Liabilities		(4,689)	(2,903)
Net cash provided by operating activities		14,123	(52,379)
Cash flows from investing activities:
Proceeds from Divestiture of Businesses		0	5,223
Payments for (Proceeds from) Businesses and Interest in Affiliates		(3,428)
Proceeds from Sales of Business, Affiliate and Productive Assets			493
Expenditures for property, plant & equipment		(11,364)	(14,232)
Payments to Acquire Businesses, Net of Cash Acquired		0	(304,661)
Other, net		(502)	(2,097)
Net cash used in investing activities		(15,294)	(315,274)
Cash flows from financing activities:
Net borrowings under revolving credit agreements		0	101,100
Purchase of treasury shares	(69)	(459)	(14,205)
Dividends paid		(16,672)	(16,675)
Other, net		4,086	2,843
Net cash provided by (used in) financing activities		(13,045)	73,063
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		(14,216)	(294,590)
Effect of exchange rate changes on cash and cash equivalents		(415)	458
Cash and cash equivalents at beginning of period					$ 471,540
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	121,458	121,458		$ 136,089
Cash and cash equivalents and restricted cash at end of period	$ 121,458	$ 121,458	$ 177,408	$ 104,377